Electric heater



Jan. 31, 1967 S 'K|NNEY 3,302,003

ELECTRIC HEATER Filed Sept. 28, 1964 l N VEN'TOR. 77/500086 5. lf/MVEY.

United States Patent 3,302,003 ELECTRIC HEATER Theodore S. Kinney, 2733 4th Ave. S-, Seattle, Wash. 98104 Filed Sept. 28, 1964, Ser. No. 399,699 7 Claims. (Cl. 219-550) This invention relates to an electric heater and, more particularly, to an elongated electric heater assembly which may be inserted into conduit or encasement means to effectively convert said pipe or encasement means into an immersed heat transfer element.

A principal object of this invention is to provide a heater insulator with a peripherally outstanding projection to be gripped by jaw means carried by a base strip to provide an anchor or attachment which is simple and easy to eife-ct at low cost and which has increased reliability regarding attachment without materially reducing the flexible nature of the base strip.

Another object of the invention is the provision of an electric heater, comprising a base strip and a series of insulators carried thereby in spaced-apart relation in which the manufacture and assembly steps employ the simplest tools and require only a relatively low order of mechanical skill by the artisan, but which at the same time is highly effective to maintain the elements of the resistance heater in appropriate spacing over a long period of hard usage.

Other objects of this invention will be more apparent during the course of the following discussion, in which is set forth the preferred form of the invention. It will be apparent to those skilled in the art that alterations and modifications of the herein disclosed invention may be made without departing from the spiritof this concept. All such alterations and modifications as fall within the appropriate scope of the subjoined claims are intended to be covered by this patent.

In the drawings:

FIGURE 1 is a cross-section of an encased electric heater according to this invention;

FIGURE 2 is a side view of an end ortion of an electric heater as it would appear partially extended from an enoasing conduit;

FIGURE 3 is an enlarged side view of a part of an electric heater;

FIGURE 4 is a perspective View showing the construc- 7 tion of the base strip;

FIGURE 5 is a perspective view of an insulator block as used in this invention; and

FIGURE 6 is a detail view showing an angular relation between insulator projection and the base strip.

Referring to FIGURE 2, an electric heater is installed in a tubular conduit 10 by endwise insertion. As an example, conduit 10 may be a pipe installed in a tank in which :asphaltic or heavy petroleum products are to be heated. Such a tube may be as long as 10, 20' or 30'. The heater comprises the base strip 12 and a plurality of insulator blocks 14, carried thereby in spaced-apart, faceto-face relation. The insulator blocks, as shown in FIG- URE 5, have a series of openings disposed around the central axis of the body of the block and coils 16 of electrical resistance wire are threaded therethrough. By grouping several blocks 18, as shown to the left in FIG- URE 2, a terminal assembly is provided for the heater. Metallic conductor bars 19 are passed through the aligned openings of the several blocks forming the terminal. Lead-in wires 20, as well as the resistance wires 16, are secured to the ends of such bars to elfectively provide a connection between the external lead wires 20 and the normally heated resistance wire 16. The terminal in- 3,302,003 Patented Jan. 31, 1967 sulator group 18 is preferably anchored to a base 17 attached to the end of strip 12.

Each of the insulator blocks 14 comprises an annular body 24 having an outwardly swelled projection 26 outstanding from its periphery on one side. The projection 26 is integral with the annular body material 24, the same usually being of ceramic origin. In its preferred form, the projection 26 is dovetail-shaped which may be easily gripped. Essentially, the projection is undercut in angular fashion between its outer larger extremity and its smaller root adjacent the block. Apertures or openings 28 are aligned with each other and with the axis of the body 24 and extend between the opposite faces of the block. While the main portion of each aperture is cylindrical, it is customary in the trade to form grooves at opposite sides of each aperture. Among other things, such grooves serve to receive terminal bars 19, as described regarding FIGURE 2.

To convey an appreciation of size and proportion, a typical insulator body may have a diameter of 2 /2", a thickness of A", and the broadest dimension of the dovetail 26 being approximately 1%". The apertures 28 are suitably about V in diameter and long. Normally a tube 10 to accommodate such an assembly will have an internal diameter of about 3 inches. All sizes may of course be varied to satisfy different requirements.

The metallic base strip 12 which receives and supports a series of insulator blocks, is shown in FIGURE 4 to comprise a laminated or superposed pair of bands 30 and 32. Band 30 has a series of jaw or clip elements 34 extending along one edge. Band 32 likewise has a similar series of clips or jaw elements 36 extending along an opposite side edge. These jaws are arranged oppositely in pairs with the bands 30, 32 in face-to-face contact. The dovetail 26 of an insulator block 14 is transversely disposed between jaw members 34, 36. When such arrangement is attained, a spot-weld 38 or other suitable fastening means joins the bands and holds them tightly laminated together. The jaw means grip the sloping surface of the insulator projections and hold the insulators and base strip assembled. In FIGURE 4, :at 38, spotwelding marks are indicated.

It is desirable that the gripping action on the dovetails be with tension. To this end the slope of the dovetail is arranged at a 45 angle to the bottom surface, as shown in FIGURE 6. And jaw 36 is bent at a slightly more acute angle, say 40", relative to its band 32. The opposite jaw 34 would likewise be so arranged. When the jaws are pressed together to grip the dovetail they are tensed and, after bands 30, 32 are secured together, remain tensed firmly gripping the insulator blocks 14. By locating the anchor means between the base strip and the insulator body wholly outside the periphery of the body, it is insured that no grounded metal may be disposed any closer to an electrical resistor than the annular body edge.

It should be understood that electric heaters, according to this invention, are largely intended for industrial application and that the voltage supplied thereto may be, for example, as high as 480-550 volts, and that the rating of the heaters may be between 1 and 24 kw.

When the heater element is installed in a pipe, normally its metal base strip rests on the lower inner surface of such pipe with the ceramic body substantially filling the remainder of the space within the pipe as shown in FIGURE 1.

What is claimed is:

1. An electric heater, comprising:

a flexible metallic base strip having a series of insulator blocks arranged therealong in spaced-apart, face-toface relation;

the blocks of said series having aligned openings receiving and supporting electrical resistance means in spaced relation longitudinally of said base strip; each insulator block having an integral, outwardlyswelled projection outstanding on its periphery; and opposed discontinuous jaw means along the side edges of said strip each gripping said insulator projections on said spaced-apart blocks.

2. The structure according to claim 1, in which the base strip comprises tWo bands laminated together, and the jaw means along one side edge are integral with one band and the jaw means along the opposite side edge are integral with the other band.

3. The structure according to claim 2, in which the laminated-together bands are secured by weldings located in the spaces between insulator blocks.

4. The structure according to claim 1, in which the projections outstanding from said insulator bodies are dovetail shaped and are disposed transverse said strip.

5. The structure according to claim 1, in which the projections outstanding from said insulator bodies are dovetail shaped and are disposed transverse said strip, and said jaw means gripping said projections are tensed.

6. An electric insulator block, comprising:

a ceramic block having opposite faces and a peripheral edge adapted to substantially conform to the internal wall of a heater pipe;

said block having axially aligned, vertically spacedapart openings extending between said faces; and

said block having an integral dovetail projection disposed symmetrically of said vertically spaced-apart openings and outstanding on said peripheral edge,

said projection being undercut between its outer extremity and its root adjacent said block edge.

7. An electric heater, comprising:

a flexible metallic base strip having a series of insulator blocks arranged therealong in spaced-apart, face-toface relation;

the blocks of said series having plural aligned openings receiving and supporting electrical resistance means in spaced relation longitudinally of said base strip;

each insulator block having an integral, outwardlyswelled dovetail projection outstanding on its periphery; and

opposed discontinuous jaw means along the side edges of said strip gripping said dovetail projections;

the angular relation between said dovetail projections and the jaw means gripping the same are enclosed to angles of lesser degree than the included angles of said dovetail surfaces.

References Cited by the Examiner UNITED STATES PATENTS 1,188,972 6/1916 Moffat 174-138.8 1,697,317 1/1929 Kyle 174l58 1,997,146 4/1935 Hynes 219550 X 2,750,487 6/1956 Hynes 219-550 X 3,043,942 7/1962 Wickwire et al. 219-550 3,136,885 6/1964 Hynes 219382 RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. AN ELECTRIC HEATER, COMPRISING: A FLEXIBLE METALLIC BASE STRIP HAVING A SERIES OF INSULATOR BLOCKS ARRANGED THEREALONG IN SPACED-APART, FACE-TOFACE RELATION; THE BLOCKS OF SAID SERIES HAVING ALIGNED OPENINGS RECEIVING AND SUPPORTING ELECTRICAL RESISTANCE MEANS IN SPACED RELATION LONGITUDINALLY OF SAID BASE STRIP; EACH INSULATOR BLOCK HAVING AN INTEGRAL, OUTWARDLYSWELLED PROJECTION OUTSTANDING ON ITS PERIPHERY; AND OPPOSED DISCONTINUOUS JAW MEANS ALONG THE SIDE EDGES OF SAID STRIP EACH GRIPPING SAID INSULATOR PROJECTIONS ON SAID SPACED-APART BLOCKS. 